The Organic Light Emitting Diode (OLED) possesses many advantages of outstanding properties of self-illumination, low driving voltage, high luminescence efficiency, fast response, high clarity and contrast, near 180° view angle, wide range of working temperature, applicability of flexible display and large scale full color display, and has been drawn a lot of attentions and is considered to be a new generation display to gradually replace the traditional displays. Thus, it has been widely applied in cellular phone screens, computer displays, full color TV, etc. The OLED display is different from the traditional liquid crystal display and the back light is not required. It utilizes an ultra thin organic material coating layer and a glass substrate, and theses organic material will illuminate when the current is conducted.
Please refer to FIG. 1, which is a sectional structure diagram of a flexible OLED according to prior art, which comprises a substrate 100, a first gate 210 and a second gate 220 separately positioned on the substrate 100, a gate isolation layer 300 positioned on the first gate 210, the second gate 220 and the substrate 100, a first semiconductor layer 410 positioned on the gate isolation layer 300 above the first gate 210, a second semiconductor layer 420 positioned on the gate isolation layer 300 above the second gate 220, an etching stopper layer 500 positioned on the first semiconductor layer 410, the second semiconductor layer 420 and the gate isolation layer 300, a first source 610, a first drain 620, a second drain 630 and a second drain 640 positioned on the etching stopper layer 500, an interlayer insulation layer 700 positioned on the first source 610, the first drain 620, the second drain 630, the second drain 640 and the etching stopper layer 500 and a flat layer 800 positioned on the interlayer insulation layer 700, a first electrode 900 positioned on the flat layer 800, a pixel definition layer 1000 having an open, positioned on the first electrode 900 and the flat layer 800, and an organic light emitting layer 1100 positioned on the first electrode 900 in the open of the pixel definition layer 1000, and a second electrode 1200 positioned on the pixel definition layer 1000 and the organic light emitting layer 1100, and a dryer layer 1300 positioned on the second electrode 1200, and a package thin film 1400 positioned on the dryer layer 1300 and the pixel definition layer 1000.
The first source 610 contacts the first semiconductor layer 410 and the second gate 220, and the first drain 610 contacts the first semiconductor layer 410, and the second source 630 contacts the second semiconductor layer 420, and the second drain 640 contacts the second semiconductor layer 420. The first gate 210, the first semiconductor layer 410, the first source 610 and the first drain 620 constructs a switch TFT T10, and the second gate 220, the second semiconductor layer 420, the second source 630 and the second drain 640 construct a drive TFT T20. The first electrode 900 contacts the second source 630. The open of the pixel definition layer 1000 exposes a portion of the first electrode 900.
The first electrode 900 is employed as being the pixel electrode, i.e. the anode of the OLED. The second electrode 1200 is employed as being the cathode of the OLED. Generally, the second electrode 1200 is thinner, and particularly in the top light emitting type OLED, the transparent cathode has to be manufacture. Thus, a thinner second electrode 1200 is demanded. However, under circumstance that the second electrode 1200 becomes thinner, the resistance is larger, and the conductivity is weaker. For the large scale OLED display, it can cause the uneven voltages for the respective pixels. The display homogeneity will be influenced and the mura issue can happen.